1. Field of the Invention
The present invention relates to novel peptide derivatives which are used as substrates for measuring the protease activities.
More particularly, this invention is concerned with peptide derivatives useful as color-developing or fluorescent substrates employed for measuring the activity of cysteine proteases in which a thiol group is essential for the exertion of the activity.
Enzymes of the group EC 3. 4. 22 are known to be cysteine proteases in which a thiol group is essential for the exertion of the activity. These enzymes are present in mammalian tissues such as muscles and liver and play an important physiological role. Therefore, measurement of the activity for these enzymes has a significance for elucidating many physiological actions in mammal tissues and is applicable to the diagnosis of diseases.
2. Description of the Prior Art
Activities of enzymes of the group EC 3. 4. 22, for example, cathepsin B [EC 3. 4. 22.1], cathepsin L [EC 3. 4. 22.-] and cathepsin H [EC 3. 44. 22.-] have been assayed with BANA (.alpha.-N-benzoyl-DL-arginine-2-naphthylamide) as a substrate. BANA, however, is of a lower sensitivity for enzymes of the group EC 3. 4. 22, and it was difficult to effect the assay with this substrate when the specimen contained only a small amount of the enzyme. Particularly for muscle specimens which contain a very small amount of the enzyme substrates of high sensitivity are desired.